I had not heard of that. Is that because of the greater time-in-barrel of the slower .38 that causes more elevation increase [flip] at exit that causes its higher trajectory?
[Please excuse the offtopickness of this query.]
Thats the theory I've heard, and it fits in what what i've seen....
As the magnums are travelling a lot faster that my target .38 loads (more than double the velocity...) the .357 is out of the barrel before its had time to rise as much as it does with the light .38 loads.... so with my Marlin 1894, which is zeroed for my target loads, a factory .357 load will shoot 3-4 inches low at 25 yds.